O'Connor, the retired Supreme Court justice who was in Chicago for a speech on judicial independence and to promote her civics education Web site, served on a panel of judges Tuesday and Wednesday hearing oral arguments in 10 appeals.

"Just knowing she was up there and looking at you while you're giving your argument was a little bit imposing," said Floss, a Chicago attorney. "It was a special treat. It's certainly something I'll remember for the rest of my life."

Introducing O'Connor to the unusually packed courtroom Wednesday, Judge Ann Claire Williams called it "indeed a special day."

O'Connor is the first retired Supreme Court justice to hear a case in the 7th Circuit in more than 30 years, said Collins Fitzpatrick, the court's circuit executive, who added he wouldn't be surprised if she writes opinions on some of the cases she heard.

O'Connor and Justice David Souter, the only two retired members of the Supreme Court, sit regularly on appeals courts to decide cases. Souter hears cases in Boston, while O'Connor travels around the country.

Attorney Jim Dasso, who has nearly 25 years' experience arguing cases, was astonished when he learned — just about 20 minutes before he was face to face with her — that he would appear before a Supreme Court trailblazer.

"It certainly upped the ante a little bit," he said.

She exuded a commanding presence and insisted on direct answers, Dasso said.

"She asked several very tough questions and wouldn't let me squirm off the hook on any of them," Dasso said.